Field of the Invention
The present invention relates to a method of regenerating porous hydrodesulfurization (HDS) catalysts having an alumina substrate or base which have been deactivated incidental to use in a hydrodesulfurization process by build-up of exogenous nickel and vanadium compounds on the surface of and in the pores of the HDS catalyst.
Copending application Ser. No. 517,027, the content of which is hereby incorporated by reference in this application, teaches a method of removing unwanted nickel and vanadium from spent HDS catalysts including pretreatment steps such as washing the spent HDS catalyst with solvent to remove residual oil, calcining the pretreated, spent HDS catalyst to remove coke and sulfiding the spent HDS catalyst, prior to leaching the spent HDS catalyst in an acidic solution containing ferric ions to solubilize metal sulfides and from which solution the regenerated HDS catalyst is recovered. The sulfiding step is taught to be essential but the other two pretreatment steps are taught to be optional.
The above application discloses such treatment both in the context of metals removal for its own sake and metals removal for regenerating the HDS catalyst.